High-gain single planar waveguide (PWG) amplifier laser system

ABSTRACT

A system includes a master oscillator configured to generate a first optical beam and a beam controller configured to modify the first optical beam. The system also includes a PWG amplifier configured to receive the modified first optical beam and generate a second optical beam having a higher power than the first optical beam. The second optical beam has a power of at least about ten kilowatts. The PWG amplifier includes a single laser gain medium configured to generate the second optical beam. The system further includes a feedback loop configured to control the master oscillator, PWG amplifier, and beam controller. The feedback loop includes a laser controller. The laser controller may be configured to process wavefront information or power in bucket information associated with the second optical beam to control an adaptive optic or perform a back-propagation algorithm to provide wavefront correction at an output of the PWG amplifier.

CROSS-REFERENCE TO RELATED APPLICATIONS AND PRIORITY CLAIM

This application is a continuation of U.S. patent application Ser. No.15/233,913 filed on Aug. 10, 2016, which claims priority under 35 U.S.C.§ 119(e) to U.S. Provisional Patent Application No. 62/259,722 filed onNov. 25, 2015. These applications are hereby incorporated by referencein their entirety.

TECHNICAL FIELD

This disclosure is generally directed to high-power laser systems. Morespecifically, this disclosure is directed to a high-gain single planarwaveguide (PWG) amplifier laser system.

BACKGROUND

High-power laser systems are being developed for a number of militaryand commercial applications. Many conventional high-power laser systemsuse one or more laser amplifier beamlines in a master oscillator/poweramplifier (MOPA) configuration. Each beamline includes multiple largeand relatively low-gain laser amplifiers that collectively provide alarge amount of gain for optical signals being amplified.

SUMMARY

This disclosure provides a high-gain single planar waveguide (PWG)amplifier laser system.

In a first embodiment, a method includes generating a first optical beamusing a master oscillator and modifying the first optical beam using abeam controller. The method also includes amplifying the modified firstoptical beam to generate a second optical beam using a PWG amplifier.The second optical beam has a higher power than the first optical beam.The method further includes controlling the master oscillator, the PWGamplifier, and the beam controller using a feedback loop that includes alaser controller. The second optical beam has a power of at least aboutten kilowatts and is generated using a single laser gain medium in thePWG amplifier.

In a second embodiment, a system includes a master oscillator configuredto generate a first optical beam and a beam controller configured tomodify the first optical beam. The system also includes a PWG amplifierconfigured to receive the modified first optical beam and generate asecond optical beam having a higher power than the first optical beam.The second optical beam has a power of at least about ten kilowatts. ThePWG amplifier includes a single laser gain medium configured to generatethe second optical beam. The system further includes a feedback loopconfigured to control the master oscillator, the PWG amplifier, and thebeam controller. The feedback loop includes a laser controller.

In a third embodiment, a non-transitory computer readable mediumcontains instructions that when executed cause a laser controller tocontrol a master oscillator, a PWG amplifier, and a beam controllerwithin a feedback loop that includes the laser controller. The masteroscillator is configured to generate a first optical beam. The beamcontroller is configured to modify the first optical beam. The PWGamplifier is configured to amplify the modified first optical beam andgenerate a second optical beam having a power that is at least about tenkilowatts and that is higher than a power of the first optical beam.

Other technical features may be readily apparent to one skilled in theart from the following figures, descriptions, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of this disclosure, reference is madeto the following description, taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 illustrates an example high-power laser system according to thisdisclosure;

FIG. 2 illustrates an example packaged high-power laser system accordingto this disclosure;

FIGS. 3 through 6 illustrate an example integrated optical bench andcooling manifold in a packaged high-power laser system according to thisdisclosure;

FIGS. 7A and 7B illustrate example coolant flow in an optical bench andcooling manifold of a packaged high-power laser system according to thisdisclosure;

FIGS. 8A through 8C and FIG. 9 illustrate additional details of anexample packaged high-power laser system according to this disclosure;

FIGS. 10A through 10C illustrate an example pump optics assembly of apackaged high-power laser system according to this disclosure;

FIGS. 11A and 11B illustrate an example planar waveguide (PWG) pumpheadassembly of a packaged high-power laser system according to thisdisclosure;

FIGS. 12A and 12B illustrate an example PWG cartridge for a PWG pumpheadassembly of a packaged high-power laser system according to thisdisclosure;

FIG. 13 illustrates an example pumphead configuration with an examplePWG cartridge for a packaged high-power laser system according to thisdisclosure;

FIGS. 14A and 14B illustrate an example pusher assembly for use with aPWG pumphead assembly of a packaged high-power laser system according tothis disclosure;

FIG. 15 illustrates example operation of a PWG amplifier of a packagedhigh-power laser system according to this disclosure; and

FIGS. 16A, 16B, and 17 illustrate example integral pumplighthomogenizers and signal injectors of a packaged high-power laser systemaccording to this disclosure.

DETAILED DESCRIPTION

FIGS. 1 through 17, described below, and the various embodiments used todescribe the principles of the present invention in this patent documentare by way of illustration only and should not be construed in any wayto limit the scope of the invention. Those skilled in the art willunderstand that the principles of the present invention may beimplemented in any type of suitably arranged device or system.

FIG. 1 illustrates an example high-power laser system 100 according tothis disclosure. As shown in FIG. 1, the laser system 100 includes amaster oscillator 102 and a planar waveguide (PWG) amplifier 104. Thelaser system 100 therefore has a master oscillator/power amplifier(MOPA) configuration.

The master oscillator 102 generally operates to generate low-poweroptical signals. The low-power optical signals could denote any suitableoptical signals having relatively low power. For example, the low-poweroptical signals could include optical signals having a continuous wave(CW) output, a continuous pulse train (CPT), a pulse burst, or any ofvarious other waveforms. The master oscillator 102 includes any suitablestructure(s) for generating one or more low-power optical signals. Insome embodiments, the master oscillator 102 includes a fiber laser.

The PWG amplifier 104 receives the low-power optical signals from themaster oscillator 102 and pump power. The PWG amplifier 104 generallyoperates to amplify the low-power optical signals and generatehigh-power optical signals. For example, the PWG amplifier 104 couldamplify a low-power CW or other optical signal into a high-power CW orother optical signal having ten kilowatts of power or more. The receivedpump power provides the necessary population inversion in the PWGamplifier's gain medium for this amplification.

The gain medium of the PWG amplifier 104 is formed using a planarwaveguide. A planar waveguide generally denotes a structure thatincludes a core region and one or more cladding layers. The core regionis doped with an active ion species responsive to optical signals of atleast one specific wavelength, and the one or more cladding layers areoptically transparent and contact the core region. The indexes ofrefraction and dielectric constants of the core region and the claddinglayer(s) differ and create boundaries that reflect the optical signals.The planar waveguide therefore operates to guide optical signals in itsnarrower dimension (referred to as the “fast axis” direction) but not inits broader dimension (referred to as the “slow axis” direction). Theplanar waveguide could be formed from any suitable materials and in anysuitable manner.

Relay optics 106 direct the optical signals from the master oscillator102 into a beam controller 108, and relay optics 110 direct the opticalsignals from the beam controller 108 into the PWG amplifier 104. Therelay optics 106 and 110 can also alter the cross-sectional dimensionsof the optical signals as needed for injection into the beam controller108 and the PWG amplifier 104, respectively. Each of the relay optics106 and 110 includes any suitable optical device(s) for directing orformatting optical signals.

The beam controller 108 generally operates to modify the optical signalsfrom the master oscillator 102 before the optical signals reach the PWGamplifier 104. For example, the beam controller 108 could pre-distortthe phase profile of the optical signals from the master oscillator 102in order to substantially or completely compensate for optical phasedistortions created within the PWG amplifier 104. The beam controller108 could also pre-distort both the amplitude and phase of the opticalsignals from the master oscillator 102. The beam controller 108 couldfurther include separate control devices for two-axis tip/tilt alignmentcontrol and higher-order beam control. The beam controller 108 includesany suitable structure(s) for pre-distorting or otherwise modifyingoptical signals in a controllable manner.

The high-power output beam generated by the PWG amplifier 104 isdirected towards a beam splitter 112. The beam splitter 112 provides asubstantial portion of the high-power output beam to relay optics 114,which provide that portion of the high-power output beam out of thelaser system 100 as a high-power output beam 116. The beam splitter 112also provides a small amount of the high-power output beam as samples toa feedback loop. The feedback loop is used to control and modifyoperation of the master oscillator 102, the PWG amplifier 104, and thebeam controller 108. The beam splitter 112 includes any suitablestructure(s) for splitting optical signals. The relay optics 114 includeany suitable optical device(s) for directing or formatting opticalsignals.

The feedback loop here includes a diagnostics unit 118, a lasercontroller 120, and diode drivers 122-124. The diagnostics unit 118generally operates to analyze the samples of the high-power output beamfrom the PWG amplifier 104. The diagnostics unit 118 includes anysuitable structure for identifying one or more characteristics of atleast one sample of a high-power output beam. For example, thediagnostics unit 118 could include a one-dimensional (1D) wavefrontsensor configured to sense phase distortions in the high-power outputbeam across the slow axis of the PWG amplifier 104. As a particularexample, a 1D Shack-Hartman sensor could include a linear cylindricallens array and a 1D semiconductor photodetector array. As anotherexample, the samples of the high-power output beam may be focusedthrough a slit in the slow axis such that only a fraction of the portionof the beam profile that is of high beam quality passes. This portioncan be sensed by a single photodetector to measure what may be calledthe 1D “power in the bucket” (PIB), which denotes far field beam qualitymeasurements. As yet another example, the samples can be split yetagain, with one part reimaged on a wavefront sensor and another partfocused through a slit onto a PIB detector. As still another example,the slit and the PIB sensor could be replaced with a linear arrayconfigured to measure the PWG exit beam profile in the slow axis.

The laser controller 120 uses data from the diagnostics unit 118 todetermine how to adjust operation of the laser system 100. For example,the laser controller 120 may include a 1D adaptive optics (AO) processorconfigured to process wavefront or PIB information and send controlcommands to a 1D beam control device within the beam controller 108. Thebeam control device could pre-distort the phasefront of the masteroscillator's output in the slow axis direction to compensate for phasedistortions created in the PWG amplifier 104. As another example, thelaser controller 120 may include or support one or more back-propagationalgorithms to adjust the pre-distortion signal for improved wavefrontcorrection at the output of the PWG amplifier 104. The laser controller120 may further include a mechanism to jump-start the wavefrontcorrection process based on other diagnostics data. Note that whileshown here as residing before the PWG amplifier 104, other or additionalbeam control functions could be located after the PWG amplifier 104 andcontrolled by the laser controller 120. If the beam controller 108includes separate control devices for two-axis tip/tilt alignmentcontrol and higher-order beam control, alignment sensors included alongthe beam path may provide additional information to the laser controller120 for use in controlling the laser beam in tip/tilt and translation.Specific examples of the types of control algorithms that could besupported by the laser controller 120 are described in U.S. ProvisionalPatent Application No. 62/266,507 filed on Dec. 11, 2015 and entitled“PLANAR WAVEGUIDE (PWG) AMPLIFIER-BASED LASER SYSTEM WITH CORRECTION INLOW-POWER BEAM PATH” (which is hereby incorporated by reference in itsentirety). The laser controller 120 can also respond to mode controlcommands from one or more external sources, such as control commands forinitiating cooling or for initiating or ceasing laser action.

The laser controller 120 includes any suitable structure for controllingoperation of a laser system. For example, the laser controller 120 couldinclude one or more processing devices, such as one or moremicroprocessors, microcontrollers, digital signal processors, fieldprogrammable gate arrays, application specific integrated circuits, ordiscrete logic devices. The laser controller 120 could also include oneor more memories configured to store instructions or data used,generated, or collected by the processing device(s). The lasercontroller 120 could further include one or more interfaces configuredto facilitate communications with other components or systems.

The diode driver 122 generates electrical drive signals that cause oneor more laser diodes (or other light sources) of the master oscillator102 to generate optical pump power for the master oscillator 102, whichcauses the master oscillator 102 to generate desired low-power opticalsignals. The diode driver 124 generates electrical drive signals thatcause laser diodes (or other light sources) of the PWG amplifier 104 togenerate optical pump power for the PWG amplifier 104, which uses thepump power to provide optical amplification. The diode driver 124 couldbe capable of operation across a range of input voltages and loadconditions while protecting expensive laser diode strings fromelectrical shorts and transients. Each diode driver 122-124 includes anysuitable structure(s) for driving any suitable arrangement of laserdiodes or other light sources. As a particular example, each diodedriver 122-124 could include (i) two parallel-arranged buck regulatorsthat receive the same input voltage and (ii) two parallel-arrangedseries resonant DC/DC converters that each receives the outputs of bothbuck regulators and are driven in quadrature (90 degrees out of phasewith each other), where the current outputs of the DC/DC converters aresummed and provided to the laser diodes of the master oscillator 102 orPWG amplifier 104.

In some embodiments, diagnostic data from the diagnostics unit 118 couldbe output by the laser controller 120, such as to one or more externaldestinations. This could allow the external destinations to monitor thehealth, status, or safety of the laser system 100. Also, in someembodiments, the laser controller 120 may run background and commandedbuilt-in-test (BIT) routines to monitor the health, status, or safety ofthe laser system 100, predict the need for unscheduled maintenance,perform start-up sequencing, and/or shut the laser system 100 down ifparameters are out of safety tolerance. Shutdown commands may also bereceived from an external source. In the event of a shutdown command,the laser controller 120 commands the master oscillator 102 and diodedrivers 122-124 to turn off, and components such as fast reflectiveshutters may be used to divert residual laser power into a cooled beamdump (not shown).

The laser system 100 can incorporate a number of novel features, whichare described below. These novel features can be used individually or inany suitable combination. One novel feature involves the use of a singlePWG amplifier 104 in a single amplifier beamline. Many conventionalhigh-power laser systems use one or more laser amplifier beamlines,where each beamline includes multiple large and relatively low-gainlaser amplifiers that collectively provide a large amount of gain foramplification. Using this conventional approach to achieve highthresholds of laser energy could require a room full of laser amplifierequipment. The size, weight, and complexity associated with multiplehigh-power solid-state amplifier elements in a conventional MOPAconfiguration are inconsistent with many applications.

Fiber lasers are capable of achieving high stimulated emission gain overa very long path by confining a signal beam being amplified within alow-order propagating mode. Beam quality is preserved in both dimensionsbecause the fiber is very lossy for any mode other than the lowest orderdue to the small numerical aperture of its waveguide. However,conventional round fibers, even those with a large mode area, typicallycannot handle average power much above one kilowatt with good beamquality. A semi-guiding high aspect ratio (SHARC) fiber laser is capableof scaling up to much higher power levels with very good beam qualitycompared to traditional round fibers. The fast axis of the SHARC fiberconfines a beam to its lowest order mode, thereby providing neardiffraction-limited beam quality in that dimension. While the slow axisis unguided, the gain is high for only the most collimated rays sinceall others experience significant loss and are not amplified for anyappreciable distance down the SHARC fiber. High beam quality istherefore preserved after amplification in the slow axis, as well.

PWG lasers guide in one axis and are lossy in the other axis, so PWGlasers provide some of the benefits of the SHARC fiber laser with theadded benefit of a more traditional manufacturing approach and morerobust crystalline components. The laser system 100 of FIG. 1 caninclude a single high-gain PWG amplifier in a MOPA configuration. ThePWG amplifier 104 could include a single planar waveguide supported,cooled, and optically pumped within a single compact pumphead. The PWGamplifier 104 inherently provides high beam quality in its guided orfast axis, so no beam correction may be needed in this axis. High-orderbeam control may be needed only in the orthogonal slow axis of the PWGamplifier 104, such as to correct for phase distortions from non-uniformcooling across the slow axis of the PWG amplifier 104 andmechanical/thermal stresses within the PWG amplifier 104 (which mayproduce index variations).

As another example novel feature, an optical bench may be used inconjunction with various components of the laser system 100. In manyconventional high-power laser systems, the optical bench represents astiff component designed to keep optical components of the laser systemsin optical alignment. Cooling is typically provided by a separatesystem. Cooling channels are not typically used in the optical benchbecause temperature differences would warp or otherwise deform theoptical bench, causing misalignment of critical optical components.

As described below, the laser system 100 could include a PWG pumpheadassembly in which optical alignment is maintained by mounting variousoptical components to the PWG amplifier 104. An integrated optical benchand cooling manifold can be used to support the overall structure and toprovide coolant to the overall structure. The optical bench could beimplemented using a baseplate that can deform with little or no effecton the alignment of the optical components. This deformation can occurdue to, for example, changes in temperature of a coolant as the coolantflows through different components and different portions of the opticalbench. Because the various optical components can be mounted to ahousing of the PWG amplifier 104 to help maintain optical alignment ofthese components, minor deformations of the optical bench may notinterfere with proper operation of the laser system 100.

As yet another example novel feature, one or more components of thelaser system 100 could be implemented as one or more cartridges that areinserted into a pumphead or attached to an optical bench. For example,the laser gain medium of the PWG amplifier 104 could be implemented inone cartridge, and the laser diodes of the PWG amplifier 104 could beimplemented in another cartridge. Moreover, one or more of thecartridges may require a high clamping force to secure the cartridge(s),and mechanisms for providing this high clamping force are describedbelow. Among other things, this cartridge-based approach allowsdifferent cartridge designs to be installed with common (possiblystandardized) mechanical, thermal, electrical, and optical interfaceswithout making any changes to the pumphead and optical bench. Also,different design teams can create and test different designs for thevarious components of the laser system 100. There may be little or noneed for one design team to wait for the development of one component ofthe laser system 100 to be completed before designing and testinganother component of the laser system 100.

As still another example novel feature, the PWG pumphead assembly couldincorporate a homogenizing element for homogenizing the pumplightsupplied by laser diodes or other light sources. The homogenizingelement can also help to manage stray light from the light sources thatdoes not properly couple into the PWG amplifier 104. This supports theinjection of a stable beam into the PWG amplifier 104 while avoidingalignment stability concerns and decreasing component counts.

The laser system 100 could incorporate any number of additional novelfeatures as needed or desired. For example, the laser system 100 coulduse the techniques disclosed in U.S. patent application Ser. No.14/661,828 and U.S. Patent Publication No. 2014/0268309 (which arehereby incorporated by reference) to cool various components of thelaser system 100, including the use of a thermal-optic interface (TOI)material. The laser system 100 could use the techniques disclosed inU.S. Patent Publication No. 2014/0268309 to suppress amplifiedspontaneous emission (ASE) within a PWG device, including the use ofbeveled edges on the PWG device. The laser system 100 could use thetechniques disclosed in U.S. patent application Ser. No. 14/682,539(which is hereby incorporated by reference), including the use ofsymmetric and asymmetric core regions in PWG devices. The laser system100 could use the techniques disclosed in U.S. patent application Ser.No. 14/749,398 (which is hereby incorporated by reference), includingthe use of asymmetric two-layer PWG devices. The PWG amplifier 104 ofthe laser system 100 could be formed using the techniques disclosed inU.S. patent application Ser. No. 14/845,916 (which is herebyincorporated by reference), including the use of radio frequency (RF)magnetron sputtering and other techniques to form PWG-based laserdevices.

Other features could also be included in the laser system 100. Forexample, finite element structural and thermal modeling of a PWGpumphead assembly in the laser system 100 could be used to determinecharacteristics of deformation modes. This could include identifyingamplitude, frequency, order, and specific modal shape of the deformationmodes under shock, vibration, acoustic, and thermal stimulation. Theprecise locations of resonant nodes and anti-nodes of the structure canbe identified, and alignment-sensitive components (such as lenses,apertures, beam splitters, light pipes, and lasing media) could beplaced at or near specified nodes or anti-nodes in the pumpheadassembly. The elements can be placed in relationship to the nodes andanti-nodes of the structure in order to optimize their performance andminimize their misalignment along critical directions and axes.

As another example, the PWG amplifier 104 could have an asymmetricplanar waveguide, where the core region is closer to a first side of theplanar waveguide than to a second side of the planar waveguide (such aswhen cladding layers on opposite sides of the core region have differentthicknesses). Different cooling techniques could be used along the firstand second sides of the planar waveguide. As particular examples, amulti-jet liquid impingement cooler could be used for direct liquidcooling of the first side of the planar waveguide. A cooler module thatuses a flow of coolant could be used to cool the second side of theplanar waveguide through a TOI material. Alternatively, one or moreplates or other cooling devices could be coupled to opposing surfaces ofthe planar waveguide.

Overall, the laser system 100 combines the benefits of fiber lasers(such as high gain with good beam quality) and bulk solid-state lasers(such as scalability) in an overall laser architecture that supports thegeneration of high-power laser outputs. The PWG amplifier 104 functionsas a lasing element that facilitates high gain over a long amplifierpath while simultaneously maintaining near diffraction-limited beamquality in one dimension (the fast axis of the PWG amplifier 104).Substantially uniform pumping of the lasing medium and substantiallyuniform cooling of the core region combine to produce a reasonablyhigh-quality beam in the transverse dimension (the slow axis of the PWGamplifier 104).

Although FIG. 1 illustrates one example of a high-power laser system100, various changes may be made to FIG. 1. For example, any singlefeature or combination of features described above could be used in thelaser system 100. As particular examples, the laser system 100 couldinclude more than one gain medium in one or more PWG amplifiers, omitthe use of an optical bench with cooling channels, omit the use of ahomogenizing element, or not support the use of cartridges.

FIG. 2 illustrates an example packaged high-power laser system 200according to this disclosure. The packaged laser system 200 includesvarious optical components and generally helps to maintain opticalalignment of those components. These components could include a lasingmedium (such as a planar waveguide), laser diode pump arrays, injectionoptics, master oscillator, adaptive optics, and beam formatting andrelay optics between these elements.

For high average-power laser systems, nearly all elements that are inclose thermal proximity to a signal beamline and certain elements thatmay catch stray pumplight need to be actively cooled, and a coolingmanifold is used to distribute coolant and maintain proper mass flowrates and hydraulic pressures. Conventional wisdom in high-power lasersystems is to segregate the alignment function (associated with anoptical bench) and the cooling function (associated with the coolingmanifold). Conventional high-power laser systems therefore oftenthermally insulate an optical bench and critical mounting hardwareattached thereto from any cooling path in order to maintain anisothermal condition within these critical components. This is becausetemperature variations across the optical bench caused by differences incoolant temperatures can cause the optical bench to warp and misalignthe optical components.

This approach is used in some conventional PWG lasers, where the opticalbench is separate from the cooling system. The optical bench isthermally insulated from any component that would cause heating due to(i) direct irradiance by a signal beam from a laser, (ii) directirradiance by pumplight from pump arrays, (iii) indirect irradiance fromscattered light, and (iv) heat conduction through mounts and othercomponents. The optical bench is kinematically mounted so that thermaldeformation of the housing to which the optical bench is mounted wouldnot cause misalignment. At low average powers, this approach iseffective and does not penalize the system severely due to size andweight impacts. However, at higher average powers, the added size andweight associated with physically- and functionally-independent opticalbench hardware and cooling manifold hardware severely impact thedesirability of these lasers for many applications.

These prior approaches present various problems in achieving a compacthigh-power laser design. For example, the size and weight associatedwith a separate thermally-isolated optical bench grow substantially asthe laser power increases. Also, critical alignment features (such asoptics and mounts) and the optical bench itself are subject to straypumplight irradiance and, without active cooling, would warp anyway.While light baffling can mitigate some of these problems, components areoften in such close proximity that it is impractical to rely on bafflingalone.

In addition, as solid-state lasers are scaled to higher average outputpowers, the problems associated with stress-free mounting of the lasingmedium, uniform cooling of the lasing medium, efficient coupling ofpumplight into the lasing medium, and efficient coupling of laser beamsinto and out of the lasing medium are exacerbated. Stressful mountingand non-uniform heating can create phase distortions in amplified beamsand can lead to damage or fracture of the lasing medium and nearbyelements. Inefficient coupling of pumplight into the lasing medium canlead to overall laser inefficiencies, and stray light can cause damageto the lasing medium and other structures. Similarly, stray laser beamscan cause damage, and the loss of power in the stray laser beamsdetracts from the output power and overall laser efficiency. As laserpowers increase, it becomes more and more important to includediagnostic elements in a laser system, such as to determine root causesfor problems and failures and to facilitate design improvements.

The packaged high-power laser system 200 of FIG. 2 incorporates adual-function optical bench and cooling manifold for use with a PWG MOPAlaser system. As shown in FIG. 2, the packaged laser system 200 includesinput optics 202, which format the low-power signal beam from the masteroscillator 102 for optimal coupling into the PWG amplifier 104. In someembodiments, the formatted signal beam is coupled into the core regionof the PWG amplifier 104 via a front-surface reflective optic asdescribed below. In other embodiments, an internal reflection prism orother suitable optical elements may be used for this purpose. Thelow-power signal beam from the master oscillator 102 can be routed usingvarious lenses, mirrors, or other optical elements along one or moreoptical paths. The input optics 202 include any suitable opticaldevice(s) for formatting a low-power signal beam. The input optics 202could, for example, represent part or all of the relay optics 110 ofFIG. 1.

A PWG pumphead housing 204 and a PWG cartridge 206 (with its coverremoved in FIG. 2), together with one or more laser diode pump arrays208, pump coupling optics 210, and a light pipe 212, implement the PWGamplifier 104. The PWG pumphead housing 204 generally encases, protects,or otherwise contains certain elements of the PWG amplifier 104associated with the lasing medium. The PWG pumphead housing 204 can becoupled to other components of the packaged high-power laser system 200to help maintain optical alignment of various components in the lasersystem. The PWG pumphead housing 204 could be formed from any suitablematerial(s) and in any suitable manner.

The PWG cartridge 206 includes the lasing medium of the PWG amplifier104, meaning the PWG cartridge 206 includes the core region and thecladding layer(s) of a planar waveguide. The PWG cartridge 206 couldalso include other features, such as one or more high-efficiency liquidjet impingement coolers, liquid microchannel coolers, or other coolingmechanisms. The PWG cartridge 206 includes any suitable structure(s)containing a planar waveguide. In some embodiments, the PWG cartridge206 is removable from the PWG pumphead housing 204, allowing differentplanar waveguides and cooling mechanisms to be easily implemented withinthe same PWG pumphead housing 204.

Pumplight is generated for delivering pump power into the planarwaveguide by the one or more laser diode pump arrays 208. The pumplightfrom the laser diode pump arrays 208 is coupled into the planarwaveguide of the PWM amplifier 104 in order to provide the populationinversion needed for optical amplification in the lasing medium. Eachlaser diode pump array 208 includes any number of laser diodes or otherlight sources in any suitable arrangement. While two laser diode pumparrays 208 are shown here, the packaged laser system 200 could includeany number of laser diode pump arrays 208.

The pumplight from the laser diode pump arrays 208 is formatted forcoupling into the planar waveguide by the coupling optics 210. Thepumplight is then coupled into the core region and/or the claddinglayer(s) of the planar waveguide using the light pipe 212. The couplingoptics 210 include any suitable optical device(s) for directing orformatting optical signals. The light pipe 212 includes any suitableoptical device for confining, homogenizing, and/or transporting opticalsignals.

During operation of the laser system 100, the low-power signal beam fromthe master oscillator 102 is amplified as it propagates through the PWGamplifier 104 based on power received from the laser diode pump arrays208. The low-power signal beam from the master oscillator 102 is guidedonly in the thin dimension or fast axis of the PWG amplifier 104.

Output fold optics 213 and output optics 214 collimate and reformat thehigh-power beam generated by the PWG amplifier 104. In this example, theoutput fold optics 213 reverse the direction of the high-power beam, andthe output optics 214 reformat the high-power beam. The output optics214 could also provide samples of the high-power beam to a diagnosticsmodule 216. The output fold optics 213 include any suitable opticaldevice(s) for redirecting a high-power signal beam. The output optics214 include any suitable optical device(s) for directing or formatting ahigh-power signal beam. The output fold optics 213 and the output optics214 could, for example, represent part or all of the beam splitter 112and the relay optics 114 of FIG. 1.

The diagnostics module 216 implements the diagnostics unit 118 of FIG. 1and measures one or more properties of the high-power output beam. Forexample, the diagnostics module 216 could generate wavefront errorand/or power-in-the-bucket beam quality measurements using samples ofthe high-power output beam. The diagnostics module 216 includes anysuitable structure(s) for identifying and/or measuring one or morecharacteristics of a high-power output beam.

A baseplate 218 is used to support various components of the packagedhigh-power laser system 200. For example, various components could beattached to the baseplate 218 to hold the components in place within thelaser system 200. The baseplate 218 could represent a portion of anoptical bench, which is described more fully below. The baseplate 218could be formed from any suitable material(s) and in any suitablemanner.

Although FIG. 2 illustrates one example of a packaged high-power lasersystem 200, various changes may be made to FIG. 2. For example, thesizes, shapes, and relative dimensions of the various components in FIG.2 are for illustration only. Also, the specific arrangement ofcomponents in FIG. 2 could vary as needed or desired.

FIGS. 3 through 6 illustrate an example integrated optical bench andcooling manifold in a packaged high-power laser system 200 according tothis disclosure. In particular, FIG. 3 shows an exploded isometric view300 of the packaged laser system 200 with its mounting features. Asshown in FIG. 3, the laser system 200 includes an optical bench andcooling manifold 302 on which other components of the laser system 200can be mounted and through which coolant can flow to cool components ofthe laser system during operation. The optical bench and coolingmanifold 302 could be formed from any suitable material(s) and in anysuitable manner.

The remaining components of the packaged high-power laser system 200 canbe implemented in a modular fashion (although this need not be thecase). An input optics assembly 304 includes the input optics 202, and apump optics assembly 306 includes the laser diode pump arrays 208 andthe coupling optics 210. A PWG pumphead assembly 308 includes the PWGpumphead housing 204, the PWG cartridge 206, and the light pipe 212. Anoutput fold assembly 310 includes the output fold optics 213, an outputcollimator assembly 312 includes the output optics 214, and adiagnostics assembly 314 includes the diagnostics module 216. Each ofthese assemblies could be designed and fabricated separately, andmultiple versions of each assembly could be available for combinationinto a single laser system 200.

An enclosure 316 and a lid 318 can be placed over the various componentsof the laser system 200. The enclosure 316 includes input and outputwindows, beam dumps, coolant paths, and other components as described inmore detail below. The enclosure 316 could be formed from any suitablematerial(s) and in any suitable manner. The lid 318 is placed over theenclosure 316 and can be sealed or otherwise secured to the enclosure316. This allows various components of the packaged laser system 200 tobe encased within a space defined by the optical bench and coolingmanifold 302, the enclosure 316, and the lid 318. The lid 318 could beformed from any suitable material(s) and in any suitable manner.

The design shown in FIG. 3 need not be an isothermal design. Rather, thedesign of the packaged laser system 200 can thermally balance thepackaged laser system 200 in order to reduce or minimize misalignment ofcritical optical components along critical alignment axes. Thermalstresses arising from a normal drop in coolant temperature as thecoolant flows through the packaged laser system 200 can be balanced tomaintain linear and angular alignment between critical elements alongcritical axes. Motion of non-critical elements, such as baffles andabsorbers, and relative motion between critical elements alongnon-critical axes need not be controlled and are allowed in order tofacilitate thermal expansion, contraction, and deformation of theoverall structure. In some embodiments, the design for a specificimplementation can be created based on computer finite element modelingand appropriate selection of materials, and kinematic techniques formounting can be employed to maintain alignment along critical axes. Asnoted earlier, various assemblies shown in FIG. 3 can be secured to thePWG pumphead assembly 308 to help maintain alignment of opticalcomponents.

FIG. 4 shows a top view of the optical bench and cooling manifold 302 ingreater detail. As shown in FIG. 4, the optical bench and coolingmanifold 302 includes a laser diode pump array mount 402 and a PWGpumphead housing mount 404. The laser diode pump array mount 402 denotesa location where the pump optics assembly 306 can be mounted on theoptical bench and cooling manifold 302. Similarly, the PWG pumpheadhousing mount 404 denotes a location where the PWG pumphead assembly 308can be mounted on the optical bench and cooling manifold 302. Each mount402-404 includes holes or other mechanisms facilitating attachment tothe respective assembly 306-308, as well as holes acting as passagewaysfor coolant. Each mount 402-404 could have any suitable size, shape, anddimensions based on the design of the respective assembly 306-308. Inthis example, the laser diode pump array mount 402 is recessed while thePWG pumphead housing mount 404 is not, although other designs could beused.

The optical bench and cooling manifold 302 also includes one or morediode array connectors 406. The diode array connectors 406 allow controlsignals, power, or other signals to be provided to or received from thepump optics assembly 306. For example, the diode array connectors 406could couple the laser diode pump arrays 208 to the diode driver 124,which allows the laser diode pump arrays 208 to be controlled in orderto control the pump power provided into the PWG amplifier 104. Eachdiode array connector 406 includes any suitable structure(s) fortransporting signals to or from one or more laser diode pump arrays.While there are two diode array connectors 406 shown on opposite sidesof the optical bench and cooling manifold 302 in FIG. 4, the opticalbench and cooling manifold 302 could include any number of diode arrayconnectors 406 in any suitable arrangement.

At least one beam dump window 408 allows residual laser power to bediverted out of the packaged high-power laser system 200. For example,the beam dump window 408 could be used in conjunction with an opticalswitch to provide a safety feature that quickly and safely blocks theoutput beam 116. The beam dump window 408 can also allow unwantedoptical power to escape the optical bench and cooling manifold 302, suchas stray beams from the laser diode pump arrays 208 that do not coupleinto the PWG amplifier 104. Each beam dump window 408 includes anysuitable structure(s) for allowing passage of optical power, such as awindow that is substantially optically transparent to the optical power.While a single beam dump window 408 is shown here, multiple beam dumpwindows could be used as described below.

A bulkhead mount 410 for a sensor connector allows at least one sensorto be coupled to the optical bench and cooling manifold 302. Forexample, the bulkhead mount 410 could allow at least one temperaturesensor to be coupled directly to the optical bench and cooling manifold302. The temperature sensor can be used to measure the temperature ofthe optical bench and cooling manifold 302 during operation and todetect unsafe or hazardous conditions associated with the packagedhigh-power laser system 200. The bulkhead mount 410 could have anysuitable size, shape, and dimensions depending on the sensor(s) beingused. While a single bulkhead mount 410 is shown here, multiple bulkheadmounts could be used.

Note that the diode array connectors 406 and the beam dump windows 408can be sealed to prevent material from leaking out of or into thepackaged laser system 200. A seal can also be used with the bulkheadmount 410 after one or more sensors are inserted into the bulkhead mount410.

FIGS. 5 and 6 show a bottom view of the optical bench and coolingmanifold 302 in greater detail. In particular, FIG. 5 shows an explodedbottom view including the optical bench and cooling manifold 302, whileFIG. 6 shows an assembled bottom view including the optical bench andcooling manifold 302.

As shown in FIGS. 5 and 6, the diode array connectors 406 can beinserted into the sides of the optical bench and cooling manifold 302.Also, a beam dump mirror 502 can be inserted into the optical bench andcooling manifold 302 and used to direct optical power through the beamdump window 408. The beam dump mirror 502 includes any suitable opticaldevice for reflecting optical power through a beam dump window.

A master oscillator cavity 504 and a laser electronics cavity 506 areformed in the optical bench and cooling manifold 302. The cavity 504 isused to hold the master oscillator 102. The master oscillator cavity 504includes a passageway 508 for a connection 510 to the master oscillator102, such as a fiber optic connection to the master oscillator 102. Theconnection 510 could couple the output of the master oscillator 102 tothe input of the input optics 202. The master oscillator 102 can bepinned or bolted on multiple pads to maintain optical data reference,although this may be unnecessary with a fiber optic connection. Thecavity 506 is used to hold various electronics used by the laser system200, such as control circuitry for controlling the overall operation ofthe laser system 200 (like the laser controller 120). Each cavity504-506 could have any suitable size, shape, and dimensions. In thisexample, each cavity 504-506 is recessed, although other designs couldbe used.

Sensor electronics 512 can be used in conjunction with laser electronicsinserted into the cavity 506. For example, the sensor electronics 512could include one or more analog-to-digital converters for convertinganalog temperature or other measurements into digital signals. Thesensor electronics 512 could also include filters, amplifiers, or othercomponents for pre-processing sensor measurements. The sensorelectronics 512 include any suitable structure(s) for processing orhandling sensor measurements.

A first cover 514 and a second cover 516 are used to help protect othercomponents of the laser system 200. For example, the first cover 514could be used to cover the master oscillator 102 inserted into thecavity 504 and the laser electronics inserted into the cavity 506. As aparticular example, the first cover 514 could represent a hermetic sealthat helps to prevent contamination of high irradiance optical surfacesfrom outgassing of the laser electronics, thereby avoiding damage to theoptical assemblies and their associated coatings. The second cover 516could be used as a waterproof shield to help prevent water or otherfluids from infiltrating the optical compartments of the laser system200 and causing damage. Each cover 514-516 could be made of any suitablematerial(s) and in any suitable manner.

First coolant port covers 518, second coolant port covers 520, and flowdiverters/sealing plates 522 are used to control the flow of coolantthrough the optical bench and cooling manifold 302. As described in moredetail below, the port covers 518-520 and flow diverters/sealing plates522 can be used to allow coolant to enter or exit and flow through theoptical bench and cooling manifold 302 in different ways as needed forparticular implementations of the packaged high-power laser system 200.Each port cover 518-520 includes any suitable structure for blocking aninlet or outlet port for coolant. Each flow diverter/sealing plate 522includes any suitable structure for diverting a flow of coolant andblocking an inlet or outlet port for the coolant.

FIGS. 7A and 7B illustrate example coolant flow in an optical bench andcooling manifold 302 of a packaged high-power laser system 200 accordingto this disclosure. The cooling paths in this particular implementationare formed when the first coolant port covers 518 are not attached tothe optical bench and cooling manifold 302, revealing a coolant inlet702 and a coolant outlet 704. The second coolant port covers 520 areattached to the optical bench and cooling manifold 302, and the flowdiverters/sealing plates 522 are inserted into the optical bench andcooling manifold 302.

As shown in FIG. 7A, in this configuration, coolant enters through thecoolant inlet 702 and travels through a passageway 706 to a channel 708.The channel 708 provides the coolant to the pump optics assembly 306 inorder to cool the laser diode pump arrays 208. After that, the coolantflows through channels 710 from the pump optics assembly 306 intopassageways 712, which lead to channels 714. The channels 714 providethe coolant to the PWG pumphead housing 204 in order to cool to the PWGamplifier 104. The coolant returns from the PWG pumphead housing 204through channels 716, where the coolant travels through a passageway 718to the coolant outlet 704.

FIG. 7B shows a cross-section of the optical bench and cooling manifold302 through the passageway 706 and the channel 708, which providescoolant to the laser diode pump arrays 208. The cross-section here showshow the coolant flows through one laser diode pump array 208 beforereturning to a conduit 720. The conduit 720 leads to one of the channels710 on the opposite side of the optical bench and cooling manifold 302.

The various passageways shown here generally extend along a length ofthe optical bench and cooling manifold 302, while the various channelsgenerally extend through the optical bench and cooling manifold 302.With the exception of the passageway 718, the channels, conduits, andpassageways 704-716 are generally balanced, meaning the channels,conduits, and passageways 704-716 are substantially symmetrical about acentral axis of the optical bench and cooling manifold 302.

In accordance with this design, coolant flows through the optical benchand cooling manifold 302, helping to cool the optical bench and coolingmanifold 302 during operation of the laser system 100. The coolant alsoflows through the pump optics assembly 306 and the PWG pumphead assembly308, helping to cool these components during operation of the lasersystem 100. This design accommodates downstream increases in coolanttemperatures caused by heat absorption as the coolant flows through thelaser system 100. Moreover, this design maintains the necessary massflow rate and pressure for efficient cooling of critical components.

Although FIGS. 3 through 6 illustrate one example of an integratedoptical bench and cooling manifold 302 in a packaged high-power lasersystem 200, various changes may be made to FIGS. 3 through 6. Forexample, the design of the optical bench and cooling manifold 302 couldvary in different ways based on the design of the laser system 200.Also, the sizes, shapes, and relative dimensions of the components couldvary according to particular needs. Although FIGS. 7A and 7B illustrateexamples of coolant flow in an optical bench and cooling manifold 302 ofa packaged high-power laser system 200, various changes may be made toFIGS. 7A and 7B. For instance, the sizes, shapes, and dimensions of thecooling channels and passageways could vary. Moreover, different flowsof coolant could be used in an optical bench and cooling manifold 302 asneeded or desired, such as by altering which coolant port covers andflow diverters/sealing plates are used. However, an optical bench andcooling manifold 302 could include only non-reconfigurable coolantflows, and the coolant port covers and flow diverters/sealing platescould be omitted.

FIGS. 8A through 8C and FIG. 9 illustrate additional details of anexample packaged high-power laser system 200 according to thisdisclosure. As shown in FIGS. 8A through 8C, the packaged laser system200 includes the optical bench and cooling manifold 302 with all of theassociated mounted components, the enclosure 316, and the lid 318. Thelid 318 and the enclosure 316 include various beam exit apertures802-806. The beam exit apertures 802-806 denote locations where thehigh-power output beam 116 can exit the packaged laser system 200.Different beam exit apertures 802-806 can be provided at differentlocations of the packaged laser system 200 in order to allow differentusages of the packaged laser system 200. Each beam exit aperture 802-806denotes any suitable structure allowing passage of a high-power outputbeam.

At least one diagnostic viewing port 808 is provided in the packagedhigh-power laser system 200. The diagnostic viewing port 808 allows anoperator or other personnel to view into the interior of the packagedlaser system 200. This may allow, for example, the personnel to manuallyverify operation of the packaged laser system 200. The diagnosticviewing port 808 could also pass infrared (IR) radiation, allowingfunctions such as spatial and temperature high-resolution IRthermography used to detect hot spots and other deleterious thermaleffects before component damage occurs. Each diagnostic viewing port 808includes any suitable structure allowing viewing into a packaged lasersystem.

In addition, an input optics access cover 810 is provided in thepackaged laser system 200. The input optics access cover 810 providesaccess to the input optics 202 of the input optics assembly 304. Theinput optics access cover 810 could be formed from any suitablematerial(s) and in any suitable manner.

In FIG. 9, the PWG pumphead assembly 308 includes a cover 902 formingpart of the PWG pumphead housing 204, where the cover 902 includesmultiple viewing ports 904. The viewing ports 904 provide a way forobserving various laser elements including the PWG device itself whilein operation. The viewing ports 904 could also pass IR radiation,allowing functions such as spatial and temperature high-resolution IRthermography used to detect hot spots and other deleterious thermaleffects before component damage occurs.

The cover 902 could be formed from any suitable material(s) and in anysuitable manner. The cover 902 could also have any suitable size, shape,and dimensions. Each of the viewing ports 904 includes any suitablestructure allowing passage of visible, infrared, or other radiation. Atleast one of the viewing ports 904 can be located to provide a view ofat least one of the ends of a planar waveguide in the PWG amplifier 104.While five viewing ports 904 are shown here, the cover 902 could includeany number of viewing ports.

Although FIGS. 8A through 8C and FIG. 9 illustrate additional details ofone example of a packaged high-power laser system 200, various changesmay be made to FIGS. 8A through 8C and FIG. 9. For example, a high-powerlaser system could be packaged in any other suitable manner. Also, thesizes, shapes, and relative dimensions of the various components inFIGS. 8A through 8C and FIG. 9 are for illustration only. In addition,the specific arrangements of components in FIGS. 8A through 8C and FIG.9 could vary as needed or desired.

FIGS. 10A through 10C illustrate an example pump optics assembly 306 ofa packaged high-power laser system 200 according to this disclosure. Asnoted above, the pump optics assembly 306 includes one or more laserdiode pump arrays 208. In this example, the pump optics assembly 306includes two laser diode pump arrays 208, although a single laser diodepump array 208 or more than two laser diode pump arrays 208 could beused.

Each laser diode pump array 208 includes an array of multiple laserdiodes 1002, where the laser diodes 1002 are stacked and retained usinga housing 1004. Any number of laser diodes 1002 could be used in eachlaser diode pump array 208. The housing 1004 could be formed from anysuitable material(s) and in any suitable manner. The housing 1004 hereincludes various channels 1006-1008 that support coolant flow throughthe pump optics assembly 306. These channels 1006-1008 could, forinstance, align with the channel 708 and conduits 720 described above.

Light from the pump optics assembly 306 can be collimated, such as byusing one or more arrays of cylindrical lenslets (not shown) in closeproximity to the laser diodes 1002. The collimated pumplight is focusedby the coupling optics 210 through one or more windows 1010 of the PWGpumphead housing 204 and into the light pipe 212. The light pipe 212homogenizes and couples the focused pumplight into the core regionand/or the cladding layer(s) of the PWG amplifier 104. In someembodiments, two sets of laser pump diode arrays 208 and coupling optics210 are used to pump the PWG symmetrically from both sides of the coreregion, although other approaches could be used. Two supports 1012 areshown here as supporting the coupling optics 210. Each support 1012could be formed from any suitable material(s) and in any suitablemanner.

Although FIGS. 10A through 10C illustrate one example of a pump opticsassembly 306 of a packaged high-power laser system 200, various changesmay be made to FIGS. 10A through 10C. For example, the sizes, shapes,and relative dimensions of the various components in FIGS. 10A through10C are for illustration only. Also, the specific arrangement ofcomponents in FIGS. 10A through 10C could vary as needed or desired.

FIGS. 11A and 11B illustrate an example PWG pumphead assembly 308 of apackaged high-power laser system 200 according to this disclosure. FIG.11A shows an isometric view of the PWG pumphead assembly 308, whichincludes the PWG pumphead housing 204, the window 1010, and the cover902 encasing the PWG cartridge 206. As shown in FIG. 11B, a beam 1102from the master oscillator 102 and beams 1104 from the laser diode pumparrays 208 are provided to the PWG cartridge 206, and the PWG cartridge206 operates to generate the high-power output beam 116. The PWGcartridge 206 includes a planar waveguide 1110, which denotes the lasingmedium for the PWG pumphead assembly 308. The PWG pumphead housing 204also includes channels 1106-1108 that support coolant flow through thePWG pumphead assembly 308. These channels 1106-1108 could, for instance,align with the channel 714-716 described above.

FIGS. 12A and 12B illustrate an example PWG cartridge 206 for a PWGpumphead assembly 308 of a packaged high-power laser system 200according to this disclosure. As shown in FIGS. 12A and 12B, the PWGcartridge 206 includes the planar waveguide 1110. The planar waveguide1110 has at least one TOI material 1202 placed in thermal contact withthe broad clad faces of the planar waveguide 1110. The exposed sides ofthe TOI material 1202 can be bonded or otherwise attached to one or morecoolers 1204, such as by using a thermally conducting epoxy. The coolers1204 include the channels 1106-1108 and are used to transport coolant tocool the PWG cartridge 206. The TOI material 1202 includes any suitablematerial facilitating the transport of heat away from a planarwaveguide. Each cooler 1204 includes any suitable structure for removingheat from a planar waveguide. In some embodiments, for example, eachcooler 1204 could denote a copper microchannel heatsink module.

FIG. 13 illustrates an example pumphead configuration with an examplePWG cartridge 206 for a packaged high-power laser system 200 accordingto this disclosure. As shown in FIG. 13, the PWG pumphead housing 204 isused to hold the PWG cartridge 206, which includes the planar waveguide1110 and the coolers 1204. The PWG cartridge 206 is held in place usingone or more pusher assemblies 1302 in the PWG pumphead housing 204. Amain body of the housing 204 could be formed from an integral piece ofmaterial, and the cover 902 can provide access to the interior of thehousing 204. A cover 1304 allows a portion of the pusher assembly 1302to extend out of the housing 204 so that the pusher assembly 1302 can beadjusted. The pusher assemblies 1302 push inward (to the left in FIG.13) in order to secure the PWG cartridge 206 in place. Each pusherassembly 1302 includes any suitable structure for applying force againsta PWG cartridge. Each cover 1304 includes any suitable structureallowing passage of a portion of at least one pusher assembly.

FIGS. 14A and 14B illustrate an example pusher assembly 1302 for usewith a PWG pumphead assembly 308 of a packaged high-power laser system200 according to this disclosure. As shown here, the pusher assembly1302 includes a nut 1402 at one end of the pusher assembly 1302 and abridge 1404 at the opposite end of the pusher assembly 1302. As can beseen in FIG. 13, the nut 1402 can remain accessible along an outersurface of the PWG pumphead housing 204, while the bridge 1404 cancontact the PWG cartridge 206. Rotating the nut 1402 either increases ordecreases the pressure placed on the PWG cartridge 206 by the bridge1404. Each pusher assembly 1302 provides a uniform and controlledpressure onto the PWG cartridge 206, such as up to 200 pounds per squareinch or more. This can be done in a compliant manner to compensate forchanges in temperature in the housing 204. The nut 1402 and the bridge1404 could each be formed from any suitable material(s) and in anysuitable manner.

The pusher assembly 1302 also includes a threaded structure 1406 and acompression sensor 1408. The threaded structure 1406 denotes anysuitable threaded device on which the nut 1402 can be located. Forexample, the threaded structure 1406 could represent a 0.375-24 setscrew or other screw reworked to have a flat point. The compressionsensor 1408 detects an amount of compression applied against thecompression sensor 1408, which can vary depending on the position of thenut 1402 along the threaded structure 1406 when the pusher assembly 1302is located within the PWG pumphead housing 204. The compression sensors1408 in multiple pusher assemblies 1302 could be used to determinewhether the pressures applied to the PWG cartridge 206 is substantiallyuniform along the length of the PWG cartridge 206. The compressionsensor 1408 includes any suitable structure for measuring compression,such as an SB-250 sensor from TRANSDUCER TECHNIQUES, LLC.

The pusher assembly 1302 further includes a spring assembly 1410, whichincludes one or more belleville washers arranged on a thimble foralignment in this example. Any suitable number of belleville washerscould be used, such as four. Note, however, that any other suitablespring assembly could be used here. In addition, the pusher assembly1302 includes a seal 1412 around a neck of the bridge 1404. The seal1412 helps to reduce or prevent leakage into or out of the interiorspace of the PWG pumphead housing 204. The seal 1412 includes anysuitable structure for reducing or preventing fluid flow, such as anO-ring.

The design of the PWG pumphead assembly 308 here integrates the PWGlasing medium (the planar waveguide 1110), the TOI material 1202, andthe PWG cooler(s) 1204 into a cartridge assembly (the cartridge 206).The PWG cartridge 206 can be supported by spring-loaded clampsimplemented using the pusher assemblies 1302. The PWG cartridge 206 canalso interface directly with the optical bench and cooling manifold 302in order to receive coolant from the optical bench and cooling manifold302 without requiring the use of external hoses or other plumbing. Bybuilding the cartridge 206 as a separate assembly, the lasing andcooling elements can be tailored to perform together, and the thermaland mechanical stresses can be minimized. Moreover, cartridgereplacement may require minimal disassembly of the packaged laser system200.

FIG. 15 illustrates example operation of the PWG amplifier 104 of apackaged high-power laser system 200 according to this disclosure. Asshown in FIG. 15, the beam 1102 from the master oscillator 102 and thebeams 1104 from the laser diode pump arrays 208 are received at theplanar waveguide 1110. The beam 1102 is coupled into the core region ofthe planar waveguide 1110, and the beams 1104 are coupled into the coreregion and/or cladding layer(s) of the planar waveguide 1110 via thelight pipe 212. The cooling channels 1106-1108 extend through the PWGpumphead housing 204 and into the coolers 1204, and the pusherassemblies 1302 extend through the PWG pumphead housing 204 and securethe PWG cartridge 206 in place. The pusher assemblies 1302 also provideadequate force to prevent leakage of coolant from the cooling channels1106-1108.

Although FIGS. 11A through 15 illustrate examples of a PWG amplifier 104of a high-power laser system and components thereof, various changes maybe made to FIGS. 11A through 15. For example, the sizes, shapes, andrelative dimensions of the various components in FIGS. 11A through 15are for illustration only. Also, the specific arrangements of componentsin FIGS. 11A through 15 could vary as needed or desired.

FIGS. 16A, 16B, and 17 illustrate example integral pumplighthomogenizers and signal injectors 1600, 1650, and 1700 of a packagedhigh-power laser system 200 according to this disclosure. The pumplighthomogenizers and signal injectors 1600, 1650, and 1700 could denote theoptics used to couple light from optical pumping sources and the masteroscillator's signal beam into a lasing medium.

As described in detail above, modern planar waveguide lasers includefeatures to create a waveguide structure confining a laser beam in thethin dimension (the fast axis) of a PWG in order to maintain a highintensity along the gain path for high amplification factors andefficient extraction of stored energy. One or more lower index claddinglayers are included on one or both sides of the core region to confinethe laser beam in the core region and to confine pumplight within thecladding layer(s) and core region to allow efficient pumping along theentire length of the PWG.

The thin dimension of the fast axis presents several challenges indesigning a high-power PWG laser. For example, pumplight needs to befocused into the thin dimension of the core/cladding with littleoverspill and with the proper beam entrance angles to allow totalinternal reflection (TIR) confinement of the pumplight within the largerguide defined by the outer surfaces of the cladding layers. At theentrance to the PWG, the pumplight needs to be reasonably uniform andnot contain hot spots, which would degrade coatings and other surfaces.As another example, the signal beam from the master oscillator 102 needsto be formatted to fit the entrance aperture of the core region, andthis beam needs to be aligned with the PWG and maintain alignment overtime when subjected to severe temperature, shock, and vibrationenvironments typical of some applications. In addition, any straypumplight not coupled into the PWG needs to be managed and not allowedto be absorbed at uncooled surfaces, particularly near the PWG endswhere there may be TOI materials that are highly absorbing or O-ringsthat are particularly susceptible to laser damage.

Conventional PWG laser designs often use simple focusing optics to relaypumplight directly into PWG core region and cladding layers. However,light from laser diode pump arrays does not necessarily have a uniformintensity distribution at the focus of the pump input optics and, bydesign, often underfills the entrance aperture of the PWG. This canresult in significant intensity non-uniformities and hot spots where thepumplight is injected into the PWG cladding layer(s). “Power in thewings” of a focused pump spot can also result in overspill of the beamonto other structures, like TOI layers and coolers. Light baffles may beused to scrape and divert some of this pumplight overspill, butalignment of baffles is often difficult, and the location of the bafflesmay not permit complete suppression even with perfect alignment.Non-uniform heating at the end of a PWG can produce thermal gradients inthe core region across the unguided direction, resulting in refractiveindex differences and optical path-length differences (OPD) across theoutput beam. The ramifications of pumplight non-uniformity, inadequatestray light management, and optical misalignments can includelower-than-predicted lasing efficiency, reduced output beam quality,degradation of components, and catastrophic damage.

Some conventional PWG amplifier designs use a small turning mirrorlocated in close proximity to high-power pump beams to inject the signalbeam from the master oscillator into the core region of a PWG. Whileeffective, this requires precision alignment of an optic in a locationwith limited access due to its proximity to the high-power pump beams.Maintaining this type of precision alignment for this optic could beproblematic in a number of applications.

The pumplight homogenizers and signal injectors 1600, 1650, and 1700 canhelp to overcome these or other problems. The pumplight homogenizers andsignal injectors 1600, 1650, and 1700 form specialized light pipeassemblies for coupling pumplight from one or more laser diode pumparrays 208 into a high aspect ratio planar waveguide. These light pipeassemblies also help to strip off stray pumplight prior to coupling intothe planar waveguide and provide highly-uniform pump beams at the planarwaveguide's input, which reduces risk of coating damage and results inreduced wavefront distortion in the PWG amplifier. These light pipeassemblies further help to couple the signal beam from the masteroscillator 102 into the PWG amplifier 104 without passing through thepump beams and provide highly-stable alignment of very closely spacedpump and signal beams. The pumplight homogenizers and signal injectors1600, 1650, and 1700 can be placed within the PWG pumphead housing 204(and therefore separated from the laser diode pump arrays 208 by thewindows 1010), which helps to reduce or minimize contamination wherebeam intensity is greatest.

As shown in FIG. 16A, the planar waveguide 1110 includes a core region1602 and one or more cladding layers 1604 a-1604 b. The core region andcladding layers are described above. In general, the signal from themaster oscillator 102 is injected into the core region 1602, while powerfrom the laser diode pump arrays 208 is injected into cladding layer(s)1604 a-1604 b and/or the core region 1602.

In the example shown in FIG. 16A, pumplight from the laser diode pumparrays 208 (the beams 1104) is focused into the end of a prismatic orother optic 1606. The optic 1606 guides the pumplight along a guidingaxis by total internal reflection. Optical coatings may be bonded ordeposited along guiding surfaces of the optic 1606 to ensure totalinternal reflection and to protect surfaces from mechanical damage.Alternatively, low-index dielectric shims may be located over guidingsurfaces of the optic 1606 to create a fluid-filled interface betweenthe optic 1606 and prismatic or other optics 1610, where the fluidensures total internal reflection. Example fluids include water,glycol-water mixtures, air, and helium. Examples of low-index dielectricshim materials include magnesium fluoride (MgF₂), fused silica, andsapphire. The pumplight rays bounce many times off the guiding surfacesso that the pumplight emerges substantially homogenized with nosignificant hot spots. The end of the optic 1606 is in close physicalproximity to the end of the planar waveguide 1110 and is sized so thatmost or all pumplight is coupled into the core region 1602 and/orcladding layer(s) 1604 a-1604 b of the planar waveguide 1110 withnegligible overspill.

The optic 1606 effectively contains the pumplight and the optics 1610effectively strip off stray light, thereby minimizing any straypumplight near the end of the planar waveguide 1110 and reducing oreliminating the need for other forms of stray pumplight management nearthe end of the planar waveguide 1110. In some embodiments, the ends ofthe optic 1610 contain reflective coatings or anti-reflective coatings.In other embodiments, the ends of the optic 1610 are ground or polished.Also, in some embodiments, the optic 1606 extends across substantiallythe full width of the planar waveguide's slow axis to providesubstantially uniform pumping of the core region 1602, therebyminimizing temperature non-uniformities and associated thermal lensingthat causes wavefront error and degrades beam quality in the amplifiedlaser beam at the output end of the planar waveguide 1110.

The signal beam 1102 from the master oscillator 102 is formatted by theexternal relay optics 110 and is folded and injected into the coreregion 1602 of the planar waveguide 1110 off a reflective surface 1608of the optic 1610. The reflective surface 1608 could have any suitableangle with respect to the longitudinal axis of the planar waveguide1110, such as a nominal angle of 45°, which allows the signal beam 1102to be introduced from the side of the pumphead assembly 308.

Each optic 1606 and 1610 includes any suitable structure for providingdesired optical modifications, such as mixing or reflection. Thereflective surface 1608 includes any suitable structure reflective to atleast the signal beam from a master oscillator. In some embodiments, theoptic 1606 denotes the core of a light pipe, and the optics 1610 denotea portion of the cladding around the core of the light pipe.

If the optic 1606 is uncoated, the optics 1610 can have a sufficientlylower index of refraction to allow total internal reflection at the mostextreme pumplight ray angles. The optics 1606 and 1610 could havevarious other coatings or features as needed or desired. For example,evanescent wave (e-wave) coatings may be applied to the guiding surfacesof the optic 1606, or side faces of the optic 1606 could be coated toallow guiding in the lateral slow-axis direction. Anti-reflection (AR)coatings may be applied to any or all input or output faces of theoptics 1610 to improve efficiency and minimize stray light reflections.Scraper mirrors, scattering surfaces, and/or cooled absorbers may beused at the entrance to the optic 1606 to catch any stray lightemanating from the laser diode pump arrays 208 and other sources, suchas reflections of stray light from other reflective or scatteringsurfaces within the pumphead assembly 308. Mounts and other surfacesthat are not actively cooled may be coated with a high reflectivitycoating such as gold, and surfaces that are actively cooled may becoated with an absorbing material to manage heat from stray pumplight.

FIG. 16B illustrates a specific implementation of the structure shown inFIG. 16A. More specifically, the pumplight homogenizer and signalinjector 1650 in FIG. 16B includes the optic 1606 and the optics 1610.In some embodiments, the optic 1606 in FIG. 16B can be formed using ahollow space containing a fluid, such as water, glycol-water mixtures,air, helium, or gas, or an evacuated space. Inner surfaces 1612 of theoptics 1610 denote highly reflective surfaces, which form two sets ofsubstantially parallel reflective surfaces. The reflective surfaces 1612could be formed in any suitable manner, such as by using a gold or otherhighly-reflective coating. Again, the optic 1606 effectively containsthe pumplight and the optics 1610 effectively strip off stray light,thereby minimizing any stray pumplight near the end of the planarwaveguide 1110 and reducing or eliminating the need for other forms ofstray pumplight management near the end of the planar waveguide 1110.

As shown in FIG. 17, the pumplight homogenizer and signal injector 1700includes an optic 1702 and an optic 1704, which could be the same as orsimilar to the corresponding components 1606 and 1610 described above.Here, however, the signal beam 1102 from the master oscillator 102passes through a third optic 1706 prior to injection into the coreregion 1602 of the planar waveguide 1110. Additional optics 1708-1710can optionally be located on the other side of the optic 1702.

An air gap 1712 separates the optics 1704-1706, and an air gap 1714separates the optics 1708-1710. The air gaps 1712-1714 have differentindexes of refraction compared to the optics 1704-1710, creating areas1716-1718 of total internal reflection. Among other things, these areas1716-1718 allow stray pumplight to be diverted to one or more beamdumps.

Various optional features described above with respect to FIGS. 16A and16B are also shown in FIG. 17, although one, some, or all of thesefeatures could be omitted from FIG. 17 if desired. These featuresinclude e-wave coatings 1720 for guiding pumplight and AR coatings 1722at the end surfaces for improved coupling of pumplight and masteroscillator signals into and out of the pumplight homogenizer and signalinjector 1700. In addition, one or more heat rejection surfaces 1724could run laterally near the input or output ends of the pumplighthomogenizer and signal injector 1700 to help remove heat from thepumplight homogenizer and signal injector 1700.

The pumplight homogenizers and signal injectors 1600, 1650, and 1700here could support integral construction where pumplight and signal beamapertures are aligned with the planar waveguide 1110 in a singlemanufacturing step. As a result, external alignment of only the beamsfrom the master oscillator 102 and the pump optics assembly 306 may berequired. Moreover, beam alignment can be inherently preserved over timeunder severe environmental conditions without maintenance.

Although FIGS. 16A, 16B, and 17 illustrate examples of integralpumplight homogenizers and signal injectors 1600, 1650, and 1700 of apackaged high-power laser system 200, various changes may be made toFIGS. 16A, 16B, and 17. For example, while the pumplight homogenizersand signal injectors 1600, 1650, and 1700 are shown here as beingsubstantially solid, various other types of light pipe assemblies couldbe supported. As a particular example, a hollow light pipe withspecialized thin film coatings for providing light guiding functionalitycould be used in place of the optic 1606 or 1702. Also, it is possiblefor a light pipe to support signal injector and light scraping functionswithout requiring support for a homogenizing function.

High-power laser systems, such as the ones described above, could beused in a large number of military and commercial applications. Thefollowing discussion provides a description of various examplecommercial applications. However, the following discussion does notlimit this disclosure to any particular applications.

High-power laser systems could find use in commercial miningapplications, such as in drilling, mining, or coring operations. Forinstance, high-power laser systems could be used to soften or weaken anearth bed prior to drilling through the earth bed using drill bits. Thiscould allow for fewer drill bit changes and extended lifetimes andreliabilities of the drill bits. Here, free-space propagation of ahigh-power laser beam from an output window of a laser system could beused, allowing deeper penetration at further distances compared toconventional fiber lasers.

High-power and high-beam quality laser systems could also find use inremote laser welding, cutting, drilling, or heat treating operations,such as in industrial or other automation settings. The use of ahigh-power and high-beam quality laser system allows the processing ofthicker materials to occur at larger working distances from the lasersystem while minimizing the heat-affected zone and maintaining verticalor other cut lines. Among other things, this helps to support welding orcutting operations where proximity to the weld or cut site is difficultor hazardous. It also helps to protect the laser system and possibly anyhuman operators from smoke, debris, or other harmful materials.

High-power laser systems could further find use in construction anddemolition operations. Example operations could include metalresurfacing or deslagging, paint removal, and industrial demolitionoperations. High-power laser systems can be used to ablate material muchfaster and safer compared to conventional operations. As a particularexample of this functionality, high-power laser systems could be used tosupport demolition of nuclear reactors or other hazardous structures.Here, the high-power laser systems could be used to cut throughcontaminated structures like contaminated concrete or nuclearcontainment vessels or reactors from long distances. This helps to avoidthe use of water jet cutting or other techniques that create hazardouswaste, such as contaminated water. It also provides improved safetysince human operators can remain farther away from contaminatedstructures being demolished.

A number of additional applications are possible. For example,high-power laser systems could find use in power beaming applications,where high-power laser beams are targeted to photovoltaic (solar) cellsof remote devices to be recharged. High-power laser systems could finduse in hazardous material (HAZMAT) applications, where the laser systemsare used to heat and decompose hazardous materials into less harmful ornon-harmful materials.

The following describes example features and implementations of ahigh-power laser system and related components according to thisdisclosure. However, other features and implementations of a high-powerlaser system and related components could be used.

In a first embodiment, a method includes generating a low-power opticalbeam using a master oscillator and amplifying the low-power optical beamto generate a high-power optical beam using a PWG. The high-poweroptical beam has a power of at least about ten kilowatts and isgenerated using a single laser gain medium in the PWG amplifier.

Any single one or any combination of the following features could beused with the first embodiment. The single laser gain medium could liewithin a single amplifier beamline of a laser system. The masteroscillator and the PWG amplifier could be coupled to an optical benchassembly. The optical bench assembly could include optics configured toroute the low-power optical beam to the PWG amplifier and to route thehigh-power optical beam from the PWG amplifier. The PWG amplifier couldinclude (i) a cartridge that contains the single laser gain medium and(ii) a pumphead housing that retains the cartridge. The pumphead housingcould be coupled to input and output optics assemblies in order tomaintain optical alignment. The method could also include controllingoperation of the master oscillator and the PWG amplifier using a lasercontroller and performing one or more BIT routines to monitor a health,status, or safety of a laser system that includes the master oscillatorand the PWG amplifier. The method could further include generatingpumplight for the PWG amplifier using one or more laser diode pumparrays and coupling substantially all of the pumplight into the lasergain medium. In addition, the method could include at least one of (i)performing adaptive optics control using a laser controller to alter atleast one of the low-power optical beam and the high-power optical beamand (ii) performing two-axis tip/tilt alignment control using the lasercontroller. The single laser gain medium in the PWG amplifier couldinclude a planar waveguide. The planar waveguide could include a coreregion and at least one cladding layer contacting the core region.

In a second embodiment, a system includes a master oscillator configuredto generate a low-power optical beam and a PWG amplifier configured toreceive the low-power optical beam and generate a high-power opticalbeam having a power of at least about ten kilowatts. The PWG amplifierincludes a single laser gain medium configured to generate thehigh-power optical beam.

Any single one or any combination of the following features could beused with the second embodiment. The single laser gain medium couldreside within a single amplifier beamline of the system. The masteroscillator and the PWG amplifier could be coupled to an optical benchassembly. The optical bench assembly could include optics configured toroute the low-power optical beam to the PWG amplifier and to route thehigh-power optical beam from the PWG amplifier. The PWG amplifier couldinclude (i) a cartridge that contains the single laser gain medium and(ii) a housing that retains the cartridge. The housing could be coupledto input and output optics assemblies in order to maintain opticalalignment. The system could also include a laser controller configuredto control operation of the master oscillator and the PWG amplifier andto perform one or more BIT routines to monitor a health, status, orsafety of the system. The system could further include one or more laserdiode pump arrays configured to generate pumplight for the laser gainmedium and optics configured to couple substantially all of thepumplight into the laser gain medium. In addition, the system couldinclude a laser controller configured to at least one of (i) performadaptive optics control to alter at least one of the low-power opticalbeam and the high-power optical beam and (ii) perform two-axis tip/tiltalignment control. The single laser gain medium in the PWG amplifiercould include a planar waveguide. The planar waveguide could include acore region and at least one cladding layer contacting the core region.

In a third embodiment, an apparatus includes a PWG amplifier configuredto receive a low-power optical beam from a master oscillator andgenerate a high-power optical beam having a power of at least about tenkilowatts. The PWG amplifier includes a single laser gain mediumconfigured to generate the high-power optical beam.

Any single one or any combination of the following features could beused with the third embodiment. The PWG amplifier could include (i) acartridge containing the single laser gain medium and (ii) a pumpheadhousing configured to receive and retain the cartridge. The pumpheadhousing could be configured to be coupled to input and output opticsassemblies in order to maintain optical alignment. The single laser gainmedium in the PWG amplifier could include a planar waveguide. The planarwaveguide could include a core region and at least one cladding layercontacting the core region.

In a fourth embodiment, a system includes a master oscillator configuredto generate a low-power optical beam. The system also includes a PWGamplifier having one or more laser diode pump arrays, a planarwaveguide, and a light pipe. The one or more laser diode pump arrays areconfigured to generate pumplight. The planar waveguide is configured togenerate a high-power optical beam using the low-power optical beam andthe pumplight. The light pipe is configured to substantially homogenizethe pumplight and to inject the homogenized pumplight into the planarwaveguide. The light pipe is also configured to inject the low-poweroptical beam into the planar waveguide.

Any single one or any combination of the following features could beused with the fourth embodiment. The light pipe could form a pumplightaperture and a low-power optical beam aperture that are aligned with theplanar waveguide. The light pipe could include a core with a first opticconfigured to guide the pumplight along a guiding axis. The first opticcould be configured to deliver the pumplight substantially homogenizedinto the planar waveguide. The light pipe could also include a claddingwith a second optic having a reflective surface, and the reflectivesurface could be configured to reflect the low-power optical beam intothe planar waveguide. Alternatively, the light pipe could also include acladding with second and third optics separated from one another by afirst gap, the first gap could form a first area of reflection, and thefirst area of reflection could be configured to reflect the low-poweroptical beam into the planar waveguide and to reflect stray pumplighttoward a first beam dump. The cladding of the light pipe could furtherinclude fourth and fifth optics separated from one another by a secondgap, the second gap could form a second area of reflection, and thesecond area of reflection could be configured to reflect stray pumplighttoward a second beam dump. Alternatively, the light pipe could includeat least two sets of substantially parallel reflective surfaces and acore located between the sets of reflective surfaces, where the core isconfigured to guide the pumplight along a guiding axis and deliver thepumplight substantially homogenized into the planar waveguide. The corecould include a gas-filled space. The light pipe could also include atleast one of one or more evanescent wave coatings applied to one or moresurfaces of the light pipe, one or more anti-reflection coatings appliedto one or more input or output faces of the light pipe, and one or moreheat rejection surfaces extending laterally near one or more input oroutput ends of the light pipe.

In a fifth embodiment, an apparatus includes a light pipe configured tosubstantially homogenize pumplight from one or more laser diode pumparrays and to inject the homogenized pumplight into a planar waveguideof a PWG amplifier. The light pipe is also configured to inject alow-power optical beam from a master oscillator into the planarwaveguide.

Any single one or any combination of the following features could beused with the fifth embodiment. The light pipe could form a pumplightaperture and a low-power optical beam aperture that are configured toalign with the planar waveguide. The light pipe could include a corewith a first optic configured to guide the pumplight along a guidingaxis. The first optic could be configured to deliver the pumplightsubstantially homogenized into the planar waveguide. The light pipecould also include a cladding with a second optic having a reflectivesurface, and the reflective surface could be configured to reflect thelow-power optical beam into the planar waveguide. Alternatively, thelight pipe could also include a cladding with second and third opticsseparated from one another by a first gap, the first gap could form afirst area of reflection, and the first area of reflection could beconfigured to reflect the low-power optical beam into the planarwaveguide and to reflect stray pumplight toward a first beam dump. Thecladding of the light pipe could further include fourth and fifth opticsseparated from one another by a second gap, the second gap could form asecond area of reflection, and the second area of reflection could beconfigured to reflect stray pumplight toward a second beam dump.Alternatively, the light pipe could include at least two sets ofsubstantially parallel reflective surfaces and a core located betweenthe sets of reflective surfaces, where the core is configured to guidethe pumplight along a guiding axis and deliver the pumplightsubstantially homogenized into the planar waveguide. The light pipecould also include at least one of one or more evanescent wave coatingsapplied to one or more surfaces of the light pipe, one or moreanti-reflection coatings applied to one or more input or output faces ofthe light pipe, and one or more heat rejection surfaces extendinglaterally near one or more input or output ends of the light pipe.

In a sixth embodiment, a method includes generating a low-power opticalbeam using a master oscillator and generating pumplight using one ormore laser diode pump arrays. The method also includes generating ahigh-power optical beam based on the low-power optical beam and thepumplight using a planar waveguide of a PWG amplifier. The methodfurther includes using a light pipe to substantially homogenize thepumplight, to inject the homogenized pumplight into the planarwaveguide, and to inject the low-power optical beam into the planarwaveguide.

Any single one or any combination of the following features could beused with the sixth embodiment. The light pipe could include a core witha first optic configured to guide the pumplight along a guiding axis.The first optic could be configured to deliver the pumplightsubstantially homogenized into the planar waveguide. The light pipecould also include a cladding with a second optic having a reflectivesurface, and the reflective surface could be configured to reflect thelow-power optical beam into the planar waveguide. Alternatively, thelight pipe could also include a cladding with second and third opticsseparated from one another by a first gap, the first gap could form afirst area of reflection, and the first area of reflection could beconfigured to reflect the low-power optical beam into the planarwaveguide and to reflect stray pumplight toward a first beam dump. Thecladding of the light pipe could further include fourth and fifth opticsseparated from one another by a second gap, the second gap could form asecond area of reflection, and the second area of reflection could beconfigured to reflect stray pumplight toward a second beam dump.Alternatively, the light pipe could include at least two sets ofsubstantially parallel reflective surfaces and a core located betweenthe sets of reflective surfaces, where the core is configured to guidethe pumplight along a guiding axis and deliver the pumplightsubstantially homogenized into the planar waveguide.

In a seventh embodiment, an apparatus includes a light pipe configuredto pass pumplight from one or more laser diode pump arrays and to injectthe pumplight into a planar waveguide of a PWG amplifier. The light pipeis also configured to inject a low-power optical beam from a masteroscillator into the planar waveguide. The light pipe is furtherconfigured to scrape stray pumplight so that the stray pumplight isredirected away from the planar waveguide.

Any single one or any combination of the following features could beused with the seventh embodiment. The light pipe could include a corehaving a first optic configured to guide the pumplight along a guidingaxis and to deliver the pumplight into the planar waveguide. The lightpipe could also include a cladding with a second optic having a firstreflective surface configured to reflect the low-power optical beam intothe planar waveguide and a second reflective surface configured toreflect the stray pumplight away from the planar waveguide.

In an eighth embodiment, an apparatus includes a PWG pumphead configuredto receive a low-power optical beam and generate a high-power opticalbeam. The PWG pumphead includes a laser gain medium, a cartridge, and apumphead housing. The cartridge is configured to receive and retain thelaser gain medium, and the cartridge includes one or more coolingchannels configured to transport coolant in order to cool the laser gainmedium. The pumphead housing is configured to receive and retain thecartridge, and the cartridge is removable from the housing.

Any single one or any combination of the following features could beused with the eighth embodiment. The apparatus could also includespring-loaded clamps configured to secure the cartridge within thepumphead housing. The spring-loaded clamps could include pusherassemblies. The pusher assemblies could be configured to providecontrolled and substantially uniform pressure onto the cartridge. Eachpusher assembly could include a bridge configured to contact thecartridge, a spring assembly coupled to the bridge, and a compressionsensor configured to measure an amount of pressure applied to thecartridge. The pumphead housing could also include a cover havingmultiple viewing ports. The viewing ports could be configured to passinfrared radiation from different portions of the laser gain medium. Thelaser gain medium could include a planar waveguide. The planar waveguidecould include a core region and at least one cladding layer contactingthe core region. The PWG pumphead could be configured to direct straypumplight that fails to couple into the planar waveguide to at least onebeam dump. The pumphead housing could be configured to be coupled toinput optics and output optics to maintain optical alignment of the PWGpumphead with the input and output optics. The one or more coolingchannels could be configured to receive the coolant from an opticalbench and cooling manifold and to return the coolant to the opticalbench and cooling manifold.

In a ninth embodiment, a system includes a laser system having a masteroscillator and a PWG amplifier having one or more laser diode pumparrays, a PWG pumphead, input optics, and output optics. The PWGpumphead is configured to receive a low-power optical beam from themaster oscillator and generate a high-power optical beam. The PWGpumphead includes a laser gain medium, a cartridge, and a pumpheadhousing. The cartridge is configured to receive and retain the lasergain medium, and the cartridge includes one or more cooling channelsconfigured to transport coolant in order to cool the laser gain medium.The pumphead housing is configured to receive and retain the cartridge,where the cartridge is removable from the housing.

Any single one or any combination of the following features could beused with the ninth embodiment. The PWG pumphead could also includespring-loaded clamps configured to secure the cartridge within thepumphead housing. The spring-loaded clamps could include pusherassemblies. Each pusher assembly could include a bridge configured tocontact the cartridge, a spring assembly coupled to the bridge, and acompression sensor configured to measure an amount of pressure appliedto the cartridge. The pumphead housing could also include a cover havingmultiple viewing ports. The viewing ports could be configured to passinfrared radiation from different portions of the laser gain medium. Thesystem could also include relay optics configured to couple pumplightfrom the one or more laser diode pump arrays into the PWG pumphead. Thelaser gain medium could include a planar waveguide. The planar waveguidecould include a core region and at least one cladding layer contactingthe core region. The PWG pumphead could be configured to direct straypumplight that fails to couple into the planar waveguide to at least onebeam dump. The pumphead housing could be configured to be coupled toinput optics and output optics to maintain optical alignment of the PWGpumphead with the input and output optics. The one or more coolingchannels could be configured to receive the coolant from an opticalbench and cooling manifold and to return the coolant to the opticalbench and cooling manifold. The master oscillator, the one or more laserdiode pump arrays, the PWG pumphead, the input optics, and the outputoptics could be modular.

In a tenth embodiment, a method includes inserting a cartridge into aPWG pumphead of a laser system. The PWG pumphead is configured toreceive a low-power optical beam and generate a high-power optical beam.The PWG pumphead includes a laser gain medium, the cartridge, and apumphead housing. The cartridge is configured to receive and retain thelaser gain medium, and the cartridge includes one or more coolingchannels configured to transport coolant in order to cool the laser gainmedium. The pumphead housing is configured to receive and retain thecartridge, and the cartridge is removable from the housing.

Any single one or any combination of the following features could beused with the tenth embodiment. The method could also include removingthe cartridge from the pumphead housing and inserting a differentcartridge containing a different laser gain medium into the housing. Themethod could further include securing the cartridge within the pumpheadhousing using spring-loaded clamps.

In an eleventh embodiment, a system includes a laser system having amaster oscillator and a PWG amplifier having one or more laser diodepump arrays, a pumphead, input optics, and output optics. The systemalso includes an optical bench and cooling manifold coupled to thepumphead. The optical bench and cooling manifold is configured toprovide coolant to the one or more laser diode pump arrays and thepumphead through the optical bench and cooling manifold. The opticalbench and cooling manifold is also configured to partially deform duringoperation of the laser system. A housing of the pumphead is coupled tothe input and output optics to maintain optical alignment of thepumphead with the input and output optics.

Any single one or any combination of the following features could beused with the eleventh embodiment. The optical bench and coolingmanifold could be configured such that thermal stresses in the opticalbench and cooling manifold arising from changes in temperature of thecoolant as the coolant flows through the optical bench and coolingmanifold are substantially balanced in order to maintain linear andangular alignment between critical components of the laser system alongcritical axes of the laser system. The optical bench and coolingmanifold could be configured to undergo thermal expansion and thermalcontraction that create motion of non-critical components of the lasersystem and that create relative motion between the critical componentsof the laser system in non-critical axes of the laser system. Criticalcomponents of the laser system could be kinematically mounted to supportalignment along critical axes of the laser system. The optical bench andcooling manifold could be coupled to the pumphead on a first side of theoptical bench and cooling manifold. The optical bench and coolingmanifold could include a first recess in an opposing second side of theoptical bench and cooling manifold. The first recess could be configuredto receive the master oscillator. The optical bench and cooling manifoldcould also include a second recess in the first side of the opticalbench and cooling manifold. The second recess could be configured toreceive the one or more laser diode pump arrays. The master oscillator,the one or more laser diode pump arrays, the pumphead, the input optics,and the output optics could be modular.

In a twelfth embodiment, an apparatus is configured for use with a lasersystem. The apparatus includes an optical bench and cooling manifoldconfigured to provide coolant to (i) one or more laser diode pump arraysand (ii) a housing of a PWG pumphead that is coupled to input and outputoptics to maintain optical alignment of the housing with the input andoutput optics. The optical bench and cooling manifold is configured tobe coupled to the housing without coupling to the input and outputoptics. The optical bench and cooling manifold is also configured topartially deform during operation of the laser system.

Any single one or any combination of the following features could beused with the twelfth embodiment. The optical bench and cooling manifoldcould be configured such that thermal stresses in the optical bench andcooling manifold arising from changes in temperature of the coolant asthe coolant flows through the optical bench and cooling manifold aresubstantially balanced in order to maintain linear and angular alignmentbetween critical components of the laser system along critical axes ofthe laser system. The optical bench and cooling manifold could beconfigured to undergo thermal expansion and thermal contraction thatcreate motion of non-critical components of the laser system and thatcreate relative motion between the critical components of the lasersystem in non-critical axes of the laser system. The optical bench andcooling manifold could be configured to be coupled to the pumphead on afirst side of the optical bench and cooling manifold. The optical benchand cooling manifold could include a first recess in an opposing secondside of the optical bench and cooling manifold. The first recess couldbe configured to receive a master oscillator of the laser system. Theoptical bench and cooling manifold could also include a second recess inthe first side of the optical bench and cooling manifold. The secondrecess could be configured to receive the one or more laser diode pumparrays. The optical bench and cooling manifold could include a firstpassageway configured to receive the coolant through an inlet, a firstchannel configured to provide the coolant from the first passageway tomultiple laser diode pump arrays, conduits configured to receive thecoolant from the multiple laser diode pump arrays, second channelsconfigured to receive the coolant from the conduits, second passagewaysconfigured to receive the coolant from the second channels, thirdchannels configured to receive the coolant from the second passagewaysand provide the coolant to the pumphead, fourth channels configured toreceive the coolant from the pumphead, and a third passageway configuredto receive the coolant from the fourth channels and provide the coolantto an outlet. The first, second, and third passageways could extendalong a length of the optical bench and cooling manifold. The first,second, third, and fourth channels could extend through the opticalbench and cooling manifold.

In a thirteenth embodiment, a method includes operating a laser systemhaving a master oscillator and a PWG amplifier having one or more laserdiode pump arrays, a pumphead, input optics, and output optics. Thepumphead is coupled to an optical bench and cooling manifold. The methodalso includes providing coolant to the one or more laser diode pumparrays and the pumphead through the optical bench and cooling manifold.The optical bench and cooling manifold is configured to partially deformduring operation of the laser system. A housing of the pumphead iscoupled to the input and output optics to maintain optical alignment ofthe pumphead with the input and output optics.

Any single one or any combination of the following features could beused with the thirteenth embodiment. The optical bench and coolingmanifold could be configured such that thermal stresses in the opticalbench and cooling manifold arising from changes in temperature of thecoolant as the coolant flows through the optical bench and coolingmanifold are substantially balanced in order to maintain linear andangular alignment between critical components of the laser system alongcritical axes of the laser system. The optical bench and coolingmanifold could be configured to undergo thermal expansion and thermalcontraction that create motion of non-critical components of the lasersystem and that create relative motion between the critical componentsof the laser system in non-critical axes of the laser system. Criticalcomponents of the laser system could be kinematically mounted to supportalignment along critical axes of the laser system. The optical bench andcooling manifold could be coupled to the pumphead on a first side of theoptical bench and cooling manifold. The optical bench and coolingmanifold could include a first recess in an opposing second side of theoptical bench and cooling manifold. The first recess could be configuredto receive the master oscillator. The optical bench and cooling manifoldcould also include a second recess in the first side of the opticalbench and cooling manifold. The second recess could be configured toreceive the one or more laser diode pump arrays. The master oscillator,the one or more laser diode pump arrays, the pumphead, the input optics,and the output optics could be modular.

In some embodiments, various functions described in this patent documentare implemented or supported by a computer program that is formed fromcomputer readable program code and that is embodied in a computerreadable medium. The phrase “computer readable program code” includesany type of computer code, including source code, object code, andexecutable code. The phrase “computer readable medium” includes any typeof medium capable of being accessed by a computer, such as read onlymemory (ROM), random access memory (RAM), a hard disk drive, a compactdisc (CD), a digital video disc (DVD), or any other type of memory. A“non-transitory” computer readable medium excludes wired, wireless,optical, or other communication links that transport transitoryelectrical or other signals. A non-transitory computer readable mediumincludes media where data can be permanently stored and media where datacan be stored and later overwritten, such as a rewritable optical discor an erasable memory device.

It may be advantageous to set forth definitions of certain words andphrases used throughout this patent document. The terms “application”and “program” refer to one or more computer programs, softwarecomponents, sets of instructions, procedures, functions, objects,classes, instances, related data, or a portion thereof adapted forimplementation in a suitable computer code (including source code,object code, or executable code). The term “communicate,” as well asderivatives thereof, encompasses both direct and indirect communication.The terms “include” and “comprise,” as well as derivatives thereof, meaninclusion without limitation. The term “or” is inclusive, meaningand/or. The phrase “associated with,” as well as derivatives thereof,may mean to include, be included within, interconnect with, contain, becontained within, connect to or with, couple to or with, be communicablewith, cooperate with, interleave, juxtapose, be proximate to, be boundto or with, have, have a property of, have a relationship to or with, orthe like. The phrase “at least one of,” when used with a list of items,means that different combinations of one or more of the listed items maybe used, and only one item in the list may be needed. For example, “atleast one of: A, B, and C” includes any of the following combinations:A, B, C, A and B, A and C, B and C, and A and B and C.

The description in this patent document should not be read as implyingthat any particular element, step, or function is an essential orcritical element that must be included in the claim scope. Also, none ofthe claims is intended to invoke 35 U.S.C. § 112(f) with respect to anyof the appended claims or claim elements unless the exact words “meansfor” or “step for” are explicitly used in the particular claim, followedby a participle phrase identifying a function. Use of terms such as (butnot limited to) “mechanism,” “module,” “device,” “unit,” “component,”“element,” “member,” “apparatus,” “machine,” “system,” “processor,”“processing device,” or “controller” within a claim is understood andintended to refer to structures known to those skilled in the relevantart, as further modified or enhanced by the features of the claimsthemselves, and is not intended to invoke 35 U.S.C. § 112(f).

While this disclosure has described certain embodiments and generallyassociated methods, alterations and permutations of these embodimentsand methods will be apparent to those skilled in the art. Accordingly,the above description of example embodiments does not define orconstrain this disclosure. Other changes, substitutions, and alterationsare also possible without departing from the spirit and scope of thisdisclosure, as defined by the following claims.

What is claimed is:
 1. A method comprising: generating a first opticalbeam using a master oscillator; modifying the first optical beam using abeam controller; amplifying the modified first optical beam to generatea second optical beam using a planar waveguide (PWG) amplifier, thesecond optical beam having a higher power than the first optical beam;and controlling the master oscillator, the PWG amplifier, and the beamcontroller using a feedback loop that comprises a laser controller;wherein the second optical beam has a power of at least about tenkilowatts and is generated using a single laser gain medium in the PWGamplifier.
 2. The method of claim 1, wherein the single laser gainmedium lies within a single amplifier beamline of a laser system.
 3. Themethod of claim 1, wherein modifying the first optical beam using thebeam controller comprises at least one of: pre-distorting the firstoptical beam to at least partially compensate for distortions createdwithin the PWG amplifier; and performing two-axis tip/tilt alignmentcontrol.
 4. The method of claim 1, further comprising: providing samplesof the second optical beam to the feedback loop; wherein the feedbackloop further comprises one or more sensors configured to identify one ormore characteristics of the samples; and wherein the laser controller isconfigured to control the master oscillator, the PWG amplifier, and thebeam controller using the one or more identified characteristics of thesamples.
 5. The method of claim 4, wherein the one or more identifiedcharacteristics of the samples comprise at least one of: phasedistortions associated with the second optical beam across a slow axisof the PWG amplifier, a power in bucket (PIB) measurement associatedwith the second optical beam, and an exit beam profile associated withthe second optical beam across the slow axis of the PWG amplifier. 6.The method of claim 1, wherein: the beam controller comprises anadaptive optic; the laser controller is configured to process at leastone of wavefront information and power in bucket (PIB) informationassociated with the second optical beam to control the adaptive optic;and the adaptive optic is configured to pre-distort a phasefront of thesecond optical beam in a slow axis direction of the PWG amplifier tocompensate for phase distortions created in the PWG amplifier.
 7. Themethod of claim 1, wherein the laser controller is configured to performa back-propagation algorithm to provide wavefront correction at anoutput of the PWG amplifier.
 8. The method of claim 1, wherein thesingle laser gain medium in the PWG amplifier comprises a planarwaveguide, the planar waveguide comprising a core region and at leastone cladding layer contacting the core region.
 9. A system comprising: amaster oscillator configured to generate a first optical beam; a beamcontroller configured to modify the first optical beam; a planarwaveguide (PWG) amplifier configured to receive the modified firstoptical beam and generate a second optical beam having a higher powerthan the first optical beam, the second optical beam having a power ofat least about ten kilowatts, the PWG amplifier comprising a singlelaser gain medium configured to generate the second optical beam; and afeedback loop configured to control the master oscillator, the PWGamplifier, and the beam controller, wherein the feedback loop comprisesa laser controller.
 10. The system of claim 9, wherein the single lasergain medium lies within a single amplifier beamline of a laser system.11. The system of claim 9, wherein the beam controller is configured toat least one of: pre-distort the first optical beam to at leastpartially compensate for distortions created within the PWG amplifier;and perform two-axis tip/tilt alignment control.
 12. The system of claim9, wherein: the feedback loop is configured to receive samples of thesecond optical beam; the feedback loop further comprises one or moresensors configured to identify one or more characteristics of thesamples; and the laser controller is configured to control the masteroscillator, the PWG amplifier, and the beam controller using the one ormore identified characteristics of the samples.
 13. The system of claim12, wherein the one or more identified characteristics of the samplescomprise at least one of: phase distortions associated with the secondoptical beam across a slow axis of the PWG amplifier, a power in bucket(PIB) measurement associated with the second optical beam, and an exitbeam profile associated with the second optical beam across the slowaxis of the PWG amplifier.
 14. The system of claim 9, wherein: the beamcontroller comprises an adaptive optic; the laser controller isconfigured to process at least one of wavefront information and power inbucket (PIB) information associated with the second optical beam tocontrol the adaptive optic; and the adaptive optic is configured topre-distort a phasefront of the second optical beam in a slow axisdirection of the PWG amplifier to compensate for phase distortionscreated in the PWG amplifier.
 15. The system of claim 9, wherein thelaser controller is configured to perform a back-propagation algorithmto provide wavefront correction at an output of the PWG amplifier. 16.The system of claim 9, wherein the single laser gain medium in the PWGamplifier comprises a planar waveguide, the planar waveguide comprisinga core region and at least one cladding layer contacting the coreregion.
 17. A non-transitory computer readable medium containinginstructions that when executed cause a laser controller in a feedbackloop to: control a master oscillator, a planar waveguide (PWG)amplifier, and a beam controller, the master oscillator configured togenerate a first optical beam, the beam controller configured to modifythe first optical beam, the PWG amplifier configured to amplify themodified first optical beam and generate a second optical beam having apower that is at least about ten kilowatts and that is higher than apower of the first optical beam.
 18. The non-transitory computerreadable medium of claim 17, further containing instructions that whenexecuted cause the laser controller to receive measurements of one ormore characteristics of samples of the second optical beam; wherein theone or more identified characteristics of the samples comprise at leastone of: phase distortions associated with the second optical beam acrossa slow axis of the PWG amplifier, a power in bucket (PIB) measurementassociated with the second optical beam, and an exit beam profileassociated with the second optical beam across the slow axis of the PWGamplifier.
 19. The non-transitory computer readable medium of claim 17,wherein the instructions that when executed cause the laser controllerto control the master oscillator, the PWG amplifier, and the beamcontroller comprise: instructions that when executed cause the lasercontroller to process at least one of wavefront information and power inbucket (PIB) information associated with the second optical beam tocontrol an adaptive optic in order to compensate for phase distortionscreated in the PWG amplifier.
 20. The non-transitory computer readablemedium of claim 17, wherein the instructions that when executed causethe laser controller to control the master oscillator, the PWGamplifier, and the beam controller comprise: instructions that whenexecuted cause the laser controller to perform a back-propagationalgorithm to provide wavefront correction at an output of the PWGamplifier.